# US 9,435,726 B2 · Dynamic and depolarized dynamic light scattering colloid analyzer

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- Number: US 9,435,726 B2
- Document ID: US9435726B2
- Status: Granted
- Kind: B2
- Application number: 14/707,146
- Filed: 2015-05-08
- Published: 2015-12-10
- Granted: 2016-09-06
- Earliest claimed: 2010-08-23
- Assignees: Scattering Solutions, Inc.
- Applicants: Scattering Solutions, Inc.
- Inventors: Anthony E. Smart; William V. Meyer; Craig J. Saltiel
- Web page: https://patentgrep.com/patent/US9435726B2

## CPC

- G01N 15/10: Investigating individual particles
- G01N 15/0211: {Investigating a scatter or diffraction pattern}
- G01N 15/1434: Optical arrangements
- G01N 21/49: within a body or fluid
- G01N 21/51: inside a container, e.g. in an ampoule (G01N21/53 takes precedence)
- G01N 2015/0222: {from dynamic light scattering, e.g. photon correlation spectroscopy}
- G01N 2015/1029: {Particle size}
- G01N 2015/103: {Particle shape}
- G01N 2201/06113: Coherent sources; lasers
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)

## Abstract

Apparatus are described for measuring the characteristics of colloidal particles suspended in transparent media by Dynamic Light Scattering (DLS) and Depolarized Dynamic Light Scattering (DDLS) into regions where conventional measurements are difficult or impractical. Matching the diameter of an illuminating beam and an intersecting diameter of a field stop image extends measurements into regions that include concentrated turbid suspensions that frequently appear so visually opaque that multiple scattering typically gives a falsely low estimate of particle size. At the opposite extreme, where insufficient signal is available to determine either or both of the translational and/or rotational relaxation times of the particles, typically where they are too small, too few, or of insufficient refractive index difference from the medium to scatter enough light, measurements can be improved by: a) using a sufficiently large aperture such that many coherence areas fall upon the detector; and b) optical homodyne amplification of the scattered signal.

## Claims

### Claim 1

A system for analyzing a specimen having a suspension of particles by light scattering, the system comprising:
a sample region configured to hold the specimen;
a light source and a focusing lens arranged to illuminate an illumination volume at the sample region, wherein the illumination volume has a first diameter;
a detector and a receiving lens system arranged to receive scattered light from at least a portion of the illumination volume, wherein the receiving lens system comprises at least one lens and an adjustable aperture located adjacent to the at least one lens and wherein setting a diameter of the adjustable aperture determines a range of scattering angles of the scattered light collected by the detector and does not change a size of the illumination volume; and
a field stop located adjacent to the detector, wherein a conjugate image of the field stop formed by the receiving lens defines a second diameter of a visible volume at the sample region, and wherein the system provides optical signals at the detector that enable characterization of particle properties at a fractional concentration of the particles in the suspension as high as 0.1 for particle sizes greater than 100 nm.

### Claim 2 (depends on 1)

The system of claim 1, wherein a first diameter of the adjustable aperture can be selected to prevent a nonlinear response of the detector.

### Claim 3 (depends on 2)

The system of claim 2, wherein a second diameter of the adjustable aperture can be selected to admit more than one speckle to the detector.

### Claim 4 (depends on 3)

The system of claim 3, wherein the detector comprises an avalanche photodiode.

### Claim 5 (depends on 1)

The system of claim 1, further including a positioning instrument arranged to hold and translate the specimen.

### Claim 6 (depends on 1)

The system of claim 1, wherein the light source comprises a semiconductor laser.

### Claim 7 (depends on 1)

The system of claim 1, further including an insertable homodyne module that directs a homodyne beam to overlap the scattered light at the detector.

### Claim 8 (depends on 7)

The system of claim 7, wherein the homodyne module includes at least one reflective surface that redirects at least a portion of light from the light source that passes through the illumination volume into the homodyne beam that overlaps the scattered light.

### Claim 9 (depends on 8)

The system of claim 8, wherein the homodyne module is part of a specimen holder that holds the specimen.

### Claim 10 (depends on 8)

The system of claim 8, wherein the homodyne module comprises at least one lens and an adjustable attenuator.

### Claim 11 (depends on 7)

The system of claim 7, further comprising a coherence monitor arranged to monitor a coherence of the light source.

### Claim 12 (depends on 11)

The system of claim 11, wherein the coherence monitor comprises a wedged optical plate and an imaging camera.

### Claim 13

A method for operating a system for analyzing a specimen having a suspension of particles by light scattering, the method comprising:
illuminating an illumination volume in the specimen with a light source;
forming a conjugate image at the specimen of a field stop that is located adjacent to a detector;
receiving at the detector, through a receiving lens system, scattered light from at least a portion of the illumination volume, wherein the receiving lens system comprises at least one lens and an adjustable aperture located adjacent to the at least one lens; and
setting a diameter of the adjustable aperture to determine a range of scattering angles of the scattered light that pass through the receiving lens system and are detected by the detector, wherein setting the diameter of the adjustable aperture does not change a size of the illumination volume, and wherein the received scattered light enables characterization of particle properties at a fractional concentration of the particles in the suspension as high as 0.1 for particle sizes greater than 100 nm.

### Claim 14 (depends on 13)

The method of claim 13, further comprising changing a penetration depth into the specimen of an intersecting point of the conjugate image of the field stop and the illumination volume.

### Claim 15 (depends on 13)

The method of claim 13, further comprising setting the adjustable aperture to a first diameter responsive to an increased concentration of particles in the specimen.

### Claim 16 (depends on 15)

The method of claim 15, wherein the first diameter avoids a nonlinear response of the detector.

### Claim 17 (depends on 15)

The method of claim 15, further comprising receiving a homodyne beam with the scattered light at the detector.

### Claim 18 (depends on 13)

The method of claim 13, further comprising setting the adjustable aperture to a second diameter larger than the first diameter responsive to a decreased concentration of particles in the specimen.

### Claim 19 (depends on 18)

The method of claim 18, further comprising receiving a homodyne beam with the scattered light at the detector.

### Claim 20 (depends on 19)

The method of claim 19, further comprising adjusting an intensity of the homodyne beam at the detector to be greater than fifty times an intensity of the scattered light at the detector.